Aluminum alloys for electric conductors



United States Patent 3,278,300 ALUMINUM ALLOYS FOR ELECTRIC CONDUCTORSKichizo Koike, Kiyotaki, Nikko, Japan, assignor to The lFurukawaElectric Company Limited, Tolryo, Japan, a corporation of Japan N0Drawing. Filed June 8, 1964, Ser. No. 373,559 Claims priority,application Japan, June 12, 1963, 38/311,424, 38/311,425, 38/321,426 4Claims. (Cl. 75-138) This invention relates to improved aluminum alloys,more particularly to heat resistant aluminum alloy conductors and highstrength heat resistant aluminum alloys for electric conductors.

Aluminum cable steel reinforced has been conventionally used foroverhead power transmission lines: however, improved heat resistance andcurrent carrying capacity of aluminum alloy conductors have long beenrequired considering special transmission conditions such as busconductors in heavy capacity power station, transmission lines having aload factor of 0.5 or less (single purpose transmission lines forconnecting thermal power station and pumping-up power station), and foremergency transmission line for two circuits parallel operation in caseof fault of a single circuit, etc. To meet the above requirements,various aluminum alloys for electric conductors have been studied, andan alloy including zirconium is disclosed in Japanese Patent No.261,993. The heat resistance of Al-Zr alloys is improved as the Zrcontent is increased, on the other hand; the electric conductivity isreduced as zirconium increases, so that addition quantity of zirconiumshould be considerably limited in order to obtain an alloy having highelectric conductivity and low ohmic loss. Within the said limitation,the heat resistance becomes very low, not adapted for the heat resistantconductive alloy conductors.

Aldrey alloys have been used for overhead power transmission as well asfor aluminum cable steel reinforced; however, being a heat treatedproduct, the said alloy needs a series of treatments in the process ofmanufacturing such as solution heat treatment-aging-wire drawing-aging,which make the alloy rather costly, and also, being an age hardeningalloy, it has a disadvantage that the continuous operation temperatureof the conductor cannot be made higher than that of an ordinary aluminumwire. As a non-heat treatable high strength aluminum alloy, Al-Mgalloys, for instance 5005 alloy, have been put into use; however, itbeing a solid solution type, it is difficult to increase its electricconductivity more than 55% when the tensile strength is not less than 25kg/mm? To increase electric conductivity, magnesium content must bereduced at the sacrifice of mechanical properties such as tensilestrength and fatigue strength.

In addition to the high heat resistance, conductivity, tensile strength,and low manufacturing cost, overhead transmission line conductor isrequired to have excellent sag-tension characteristics, vibrationfatigue strength, creep characteristics, etc.

The principal object of the invention is to obviate the defects of theconventional conductors and to provide aluminum base alloys havingincreased electric conductivity and substantially equivalent heatresistance to that of the conventional heat resisting conductive alloys,

Another object of the invention is to provide aluminum alloys havinghigh mechanical strength, high heat resistance and conductivity byimproving the mechanical strength of conventional heat resistantaluminum alloy conductors.

A further object of the invention is to provide non-heat treatablealuminum alloys having excellent strength and high conductivity to bemanufactured by the same process as ordinary aluminum conductors.

In order to attain the above objects, various researches were made onmany multi-element alloys and the inventor has succeeded in obtainingaluminum alloys which have (1) high conductivity and heat resistance, or(2) high conductivity and heat resistance and substantially excellentmechanical strength, or (3) much higher conductivity than conventionalheat resistant Al-alloys or high strength Al-alloys by adding toaluminum Misch metal having any composition of one or more of rare earthmetals such as cerium or lanthanum (hereafter abridged as Re) andfurther a small amount of iron and also by adding to saidaluminum-Re-iron alloy, a suitable quantity of zirconium or magnesiumdepending on the objects of use.

The essential ingredients of the alloys of the invention consist of(Ll-0.5% of iron, 06-30% of Re, and the remainder of aluminum. Thereason for limiting the iron and Re contents to the above values in theinvention is that for iron and Re contents of less than 0.1% and 0.6%respectively, heat resistance increase is not effective and that foriron content of more than 0.5%, heat resistance increase is saturated,which may possibly deteriorate electric conductivity and corrosionresistance.

The preferable composition of the alloys of the invention is 0.6l.5% ofRe, 0.15-0.25 of iron and the remainder of aluminum.

To improve the heat resistance of said ternary conductive aluminumalloys of Al-Fe-Re, the effect of addition of quaternary element wasthoroughly investigated, and it has been ascertained that the additionof a small quantity of zirconium is very effective. The alloy developedwas composed of 06-30% of Re, (ll-0.5% of iron, 0.0 10.1% of zirconiumand the remainder of aluminum. The reason for limiting the zirconiumcontent of 0.0 1-0.1% is that at less than 0.01% of zirconium, heatresistance increase is not effective and that at more than 0.1%, theheat resistance increase is saturated while electric conductivity isreduced to less than 58% of I.A.C.S. and is unsuitable for conductorapplication.

The preferred composition of said alloy is 0.6-1.5% of Re, 0.150.25% ofiron, 0.04-0.06% of zirconium and the remainder of aluminum.

The tensile strength of the aluminum conductor made of said alloys ofthe invention consisting of Al-Fe-Re or Al-Fe-Re-Zr is substantially thesame as that of EC. grade aluminum (99.60 Al) conductor. As a result offurther research to develop a high strength heat resistant aluminumalloy, the inventor has found that addition of a small quantity ofmagnesium to Al-Fe Re alloy increases the mechanical strength withoutimpairing electric conductivity and heat resistance. That is, the alloydeveloped consists of 0.10.5% of iron, 0.63.0% of Re, 0.020.6% ofmagnesium and the remainder of aluminum. A magnesium content of 0.020.l%greatly improves the characteristics of heat resistant high strengthaluminum alloy;

a magnesium content of 0.10.6% improves characteristics of high strengthheat resistant conductive aluminum alloy. The alloys of the inventioncan be grouped into two categories, namely, an alloy consisting of0.10.5% of iron, 0.63.0% of Re, 0.020.1% of magnesium and the remainderof aluminum, and an alloy consisting of 0.10.5% of iron, 06-30% of Re,0.10.6% of magnesium and the remainder of aluminum.

When the Fe-Re-Mg-Al alloy wire is compared with the conventional 5005wire and Aldrey alloy or 6201 wire, the alloy of the invention has about35% higher electric conductivity than conventional ones for the sametensile strength, and has higher tensile strength for the same electricconductivity.

Tensile Electric strength conductivity (kg/mm?) (I.A.C.S.,

percent) Conductor of the alloy of the invention- G3 5005 alloyconductor 24 55 Aldrey alloy conductor-.. 32

To the aluminum base metal of 99.99% purity, 0.01% and 0.25% of ironwere added, and, to each mixture, 024.0% of Re was added. Cast 4 X 4.5wire bars of the composition indicated in Table 4 were hot rolled to 13mm. dia. redrawn rod and were drawn into 4.0 mm. dia. wire by ordinaryworking methods, and the tensile strength was measured after heating itat 150 C. for 1 hour. The rate of increase and decrease of the tensilestrength was compared with the value measured at the beginning of thetest. The results are shown in Table 1.

No'rE.Rc used had the following composition:

Cerium 45% Lanthanum 35% Neodymium... 15% 93% Praseody1niun1 4% SamariumRemainder Iron- 5% Magnesium, Silic 2% As seen from the above table, theanti-softening characteristic on heating is greatly improved by adding alittle amount of iron, and, for Re content of more than 0.6%, the alloyis hardened by heating. The lower limits of iron and Re were, therefore,taken as 0.1% and 0.6% respectively.

4- EXAMPLE 2 By the use of alloys having a composition shown in Table 2,Wires were produced through the process of casting-rolling-% wirerod-wire drawing-2.9 mm. dia. The conductivity and tensile strength ofdrawn wires are shown in Table 3.

The above samples were further subjected to heating at C., C., C., C.,and 220 C., for 2 hours each, and then the tensile strengths weremeasured to obtain the rate of increase and decrease. The results areshown in Table 4.

Table 4 100 0. 130 0. 160 C. i 190 C. I 220 C.

Pcrcent Percent Percent Percent Percent Judging from Tables 3 and 4, thehardening characteristic on annealing increases as the Re contentincreases, and, for the same Re content, Fe 0.5% has less hardening thanFe 0.25%. In case the conductivity is higher than 58% I.A.C.S., theupper limits for the iron and Re contents are limited to 0.5% and 3.0%respectively.

It seems that the alloy of the invention being hardened by heatinginstead of softening is due not to simple precipitation hardening but toa particular phenomenon related to the reciprocal action between soluteforeign atoms and dislocations caused by cold working.

EXAMPLE 3 Alloys having the composition of Table 5 were made into wiresof 3.2 mm. dia. to compare their characteristics with those of conductorgrade aluminum wire with regard to conductivity, tensile strength,anti-softening characteristic on heating, and creep characteristic; theresults are shown in Table 6.

Table It is apparent from comparison of Table 4 and the above tablesthat the anti-softening characteristic after Fe Si Re A1 heating ofAl-Fe-Re alloy is greatly improved by adding Name otalloy (pcr- (per-(pcr- (percent) a small quantity of zirconium, and the effects areparcem) cont) cent) 5 ticularly remarkable in the high temperature zone.

Aluminum alloy wire of the EXAMPLE 5 mventlon' 0 6 R m The quaternaryalloys consisting of Fe-Re-Zr-Al in the naindcr.

2.0 Do. proportion shown 1n Table 9 were made into wires of 3.0 Do.Conductor grade alum 10 2.9 mm. dra. to measure the tensile strength andcon wire 0.18 0.08 Do. ductivity at room temperature and to determinethe rate of increase and decrease in tensile strength by measuring Table6 Electric Tensile Rate of Creep Name of Alloy conducstrength increaseand charactivity (kg/mm?) decrease teristic (percent) (percent)(percent) Aluminum alloy wire of the invention:

01. s 18. 2 +1.1 0. 04 60.2 19. 8 +3. 5 0. 021 (16 5s. 5 21. 0 +13. 0 0.012 Conductor grade aluminum wire"-.. 62. 4 17. 9 +6. 2 0. 074

The rate of increase and decrease is expressed in terms tensile strengthafter heating them at 120 C. for days of a ratio of the tensile strengthafter the wire is heated and by measuring the same strength aftercooling them at C. for 500 hours to the tensile strength at room down toroom temperature. The results are shown in temperature before heating.The creep characteristic is Table 10.

Table 9 Zr Re Fe Si Mg Name f alloy (per- (per- (per- (per- (per- Al(percent) cent) cent) cent) cent) cent) Aluminum alloy conductor of theinvention:

(23) 0. 02 0. 7 Remainder.

0.04 0.7 Do. 5 0. 05 2.0 Do. Ordinaryaluminum conducton. Do. 5005 alloyconductor Do. Aldrey alloy conductor Do.

a strain after the wire is subjected to a stress of 27 Table 10 kg./mm.and heating at 110 C. for 100 hours.

It is clear from the above table that the aluminum alloy conductor ofthe invention has a higher conductivity Electric and a betteranti-softening characteristic after heating for 5 Tensile conducanddelong time, and more excellent creep characteristics at high Name 01figfggg g 253 temperatures than conventional aluminum conductor. (strenth) EXAMPLE 4 Quaternary alloys consisting of Fe-Re-Zr-Al in the rAluminum conductor the proportion shown in Table 7 were made into wiresof 2.9 inventivm (23) 21. 8 00. 3 +4. 8 mm. dra. by ordinary workingmethods to measure their 220 m8 +9.3 conductivity and tensile strength,and the results are or (ig) ?3-2 $2 shown in Table 7. The rates ofincrease and decrease of 5005 'i i 0 5: 'Igfg tensile strength afterheating at the predetermined temp Aldrey alloy conductor 5&2 peraturefor 2 hours are shown in Table 8.

Table 7 Electric Fe Re Zr conduc- Tensile (per- (pcr- (per- Al (percent)tivity strength cent) cent) cent) (I.A.C.S., (kg/mm?) percent) Table 8It is apparent from the above tables that the conductivity and heatresistance of the quaternary Fe-Re-Zr-Al 100C C, 4 C. C. l 220C- alloyare greatly improved compared with conventional 70 heat resistingaluminum alloys (5005 alloy and Aldrey Percent Pefielntz Page? P35321251Percent3 ll 5. 17.2 +123 16 9a EXAMPLE 6 77 +151 .70 .5 its +104 +8.111.1 -1e.9 The aluminum alloy conductors of the invention conga: 3 313;;75 sisting of Mg-Fe-Re-Al in the proportion shown in Table 1 1 werecompared with the conventional 5005 alloy con- 7 ductor (both in 2.9 mm.dia. wire form) with respect to tensile strength and electricconductivity. The results are shown in Table 11.

It is apparent from the the above table that the aluminum alloy of theinvention maintains substantially the same tensile strength at 150 C. asat room temperature.

It is clearly shown in the above tables that the tensile strengths ofthe 5005 alloy and the alloys of the invention are substantially thesame but that the electric conductivity of the latter alloys is farbetter than that of the former.

The rates of tensile strength decrease for the above aluminum alloyconductor of the invention, Aldrey alloy EXAMPLE 7 The alloys havingcomposition shown in Table 14 were cast into 4" x 4.5" wire bars whichwere hot rolled by a rod mill into bars and then redrawn into 2.9 mm.dia. wires to measure their tensile strength and electric conductivityat room temperature. The results are shown in Table 14.

Table 14 Mg Re Fe Tensile Electric (per- (per- (per- Al (percent)strength conduccent) cent) cent) (kg/mm?) tivity (percent) 0. 2 0. 15Remainder 24. 4 60. 7 0.2 0.6 0.15 .do 25.8 59.3 0. 2 1. 26. 8 58. 8 0.2 2. 0 28. 7 57. 3 0. 4 25. 8 57. 8 0. 4 0. 6 28. 2 56. 7 0. 4 1. U 29.56. 2 0. 4 2. 0 31. 7 55. 0 0. 6 l 27. 4 54. 0 0. 6 0 6 20. 4 54. 40.6 1. 0 30. 5 54. 1 0.6 2. 0 32. 5 52. 5

conductor, and 5005 alloy conductor were measured after heating them at120 C. The results are shown in Table Besides, the above aluminum alloyconductor of the invention consisting of said quaternary elements havingdiameter of 2.9 mm. was compared with a conventional heat resistantaluminum conductor by measuring their tensile strength after heating at150 C. for minutes. The results are shown in Table 13.

It is apparent from the above table that the Work hardening effect ofAl-Mg alloys increases as Re content increases and the tensile strengthincreases 3-3.5 kg./rnrn. per Re 1% independent of the Mg content in thealloy prior to the addition. The electric conductivity decreases indirect proportion to Re content in the alloy, but the rate of decreaseis as small as l.11.4% I.A.C.S. In other words, in Al-Re-Fe-Mg alloy,the tensile strength can be improved by 2.2 kg./mm. at the loss ofconductivity of 0.8%, while, in Al-Mg alloy, tensile strengthimprovement of 1.4-1.6 kg/mm. is accompanied with the loss ofconductivity by 24-29%. Thus, the alloy of the invention improvesmechanical strength and electric conductivity greatly.

EXAMPLE 8 The alloys having composition shown in Table 15 were made intowires of 2.9 mm. dia. It is clearly shown in Table 15 that theworkability for wire drawing and bendability decrease as Mg content andRe content increase.

Table 13 Tensile Rate of Mg Re Fe Zr strength increase Name of alloy(per- (per- (per- (per- A1 (percent) at room and decent) cent) cent)cent) temp. crease (kg/mm?) (percent) Hgat resistant aluminum eon- 0.150. 1 Remainder 18 21 uctor. Aluminum conductor of the in- 0.05 0. 6 0.25do 23 +1.

vention (28). 8

9 10 Table 15 Besides, by adding 0.02-0.1% of magnesium to the Fe-Re-Alalloys, the mechanical strength, heat resistance Mg Re Fe Bending andelectric conductivity thereof are greatly improved. w s g g ga A1 (p g gBesides, the addition of 0.1-0. 6% of magnesium to the n Fe-Re-Al alloyshas great effect of considerably increasing the mechanical strength ofthe original alloys without 8% g 8; Remainder": i B affecting theelectric conductivity.

g g What I claim is: 3 3 D 1. Heat resistant aluminum alloy for electricconducg; i 8. 1 3g tor consisting of 0.1-0.5%, preferably 0.15-0.2570,of 4 20 D iron, 06-30%, preferably 06-15%, of Misch metal, 0.8 4 0. 2550 D and the remainder of aluminum.

2. Heat resistant aluminum alloy for electric conduc- Here, D Stands forthe diameter of the wire, and the tor conslsting of 0.1-0.5%, preferably0.15 O.25%, of l iron, (LG-3.0%, preferably 0.6-1.5%, of Misch metal,larger the rnultlple is, the smaller the bendabihty.

-0.0l-0.1%, preferably 0.040.06%, of zirconium, and Accordingly, theadditions of Mg and Re are limited the remainder of aluminum 3 i g g m gi the angle of Wire 3. High strength heat resistant aluminum alloy forrawmg Wor a an en a electric conductor consisting of (ll-0.5%,preferably 0.15-0.25% of iron 0.6-3.0% preferably 0.61.5% of s EXAMPLE 9Misch metal, 0.02-0.1%, preferably 0.04 0.os%, of The quaternary alloysof Mg-Re-Fe-Al having commagnesium, and the remainder of aluminum.position shown in Table 16 were compared with the 4. High strengthaluminum alloy for electric conducconventional Aldrey alloy with regardto tensile strength, tor consisting of 0.1O.5%, preferably 0.150.25%, ofelectric conductivity and the rate of decrease in tensile iron, 06-30%,preferably 06-15%, of Misch metal, strength after heating at 120 C. for1,000 hours. The (ll-0.6% of magnesium, and the remainder ofalumiresults are shown in Table 16. num.

Table 16 Mg Re Fe Si Tensile Electric Rate of Name of alloy (per (per-(per- (perstrength conducdecrease cent) cent) cent) cent) (kg/mm?)tivity (percent) (percent) Aldrey alloy T 0.5 0.15 0.5 33 52 23 It willbe apparent from the above table that the alu- References Cited by theExaminer minum alloy of the invention has very high electricconductivity and anti-softening characteristic compared with UNITEDSTATES PATENTS the publicly known heat resistant aluminum alloy.3,063,832 11/1962 Snyder 75-138 Of the aluminum alloys of the inventions expl ln 3,113,991 12/1963 Kleber 75-147 above in detail, the ternaryFe-Re-Al all ys hav better 3,199,979 8/1965 Martin 75 147 electricconductivity, tensile strength, anti-softening char- 3,241,953 3 /1966Pryor et aL 75 138 acteristic and creep characteristic than the ordinaryaluminum conductor, while the quaternary Fe-Re-Zr-Al al- D AVID L RECK,Primary Examiner.

loys have better heat resistance and electric conductivity than theconventional heat resistant aluminum alloys.

R. O. DEAN, Assistant Examiner.

1. HEAT RESISTANT ALUMINUM ALLOY FOR ELECTRIC CONDUCTOR CONSISTING OF0.1-0.5%, PREFERABLY 0.15-0.25%, OF IRON, 0.6-3.0% PREFERABLY 0.6-1.5%,OF MISCH METAL, AND THE REMAINDER O ALUMINUM.